Food Safety Facts on Scombroid Poisoning

What is scombroid poisoning?

Scombroid poisoning is an allergic-type reaction to high levels of histamine in fish.

When certain fish, especially scombroid fish, start to decompose, histidine, a naturally-occurring amino acid, is converted into histamine. Histidine is converted into histamine by an enzyme produced by certain bacteria.

Histamine, in small doses, is necessary for the proper functioning of the human immune system. However, when some people are exposed to histamine in high doses, it may trigger severe allergic reactions.

The presence of high levels of histamine in fish always indicates that decomposition has occurred, even if the decomposition is not obvious. Toxic amounts of histamine can form before a fish smells or tastes bad.

What are the symptoms of scombroid poisoning?

The most commonly reported symptoms of scombroid poisoning include the following:

  • burning throat
  • diarrhea
  • dizziness
  • facial swelling
  • flushed skin
  • headache
  • itchy skin
  • nausea
  • palpitations
  • peppery taste in the mouth
  • rash
  • stomach pain
  • tingling
  • vomiting

Symptoms can occur immediately after, or several hours after, eating food with high levels of histamine. They typically last for a few hours but, in certain cases, they can last for several days. People with scombroid poisoning may also need antihistamines.

What are the sources of scombroid poisoning?

The most common source of scombroid poisoning is fish of the Scombridae and Scomberesocidae families. They are known as "scombroid fish" and include tuna, bonito and mackerel.

These fish have large amounts of free histidine that may be converted to histamine during storage.

Scombroid poisoning can also be caused by

  • marlin and fish of other families, such as Clupeidae (herring, sardines),
  • Coryphaenidae (mahi-mahi), or
  • even other foods such as cheese.

What can I do to protect myself and my family against scombroid poisoning?

Histamine formation in fish depends on the temperature at which the fish is kept from the time it is caught until it is consumed. So to avoid scombroid poisoning, it is very important to keep fish refrigerated when it is being transported and stored.

Cooking or other heat treatments (such as canning or smoking) do not destroy histamine.

Buy seafood from reputable sources to ensure that products are properly chilled. Retail employees should be able to answer questions on freshness.

If you think you have symptoms of scombroid poisoning, consult your doctor.

What is the CFIA's role in protecting consumers?

The CFIA regulates the processing of fish in all federally registered fish processing plants. All processing plants that ship product from one province to another, or export to other countries, must be registered with the CFIA.

Fish plants are required to have a quality management program (QMP), where the plant must assume responsibility for ensuring that their facilities and products meet federal quality and safety requirements.

  • Each plant must develop its own QMP that identifies critical points in the processing chain where control measures must be in place to ensure that products comply with regulatory standards.
  • CFIA inspectors regularly verify QMPs to see if they meet the requirements of the Fish Inspection Regulations.

The CFIA also monitors imports of fish products and conducts regular inspections.

  • Importers are responsible for ensuring that their products meet Canadian regulatory requirements including the food safety standards established by Health Canada (which are the same as for domestic products).
  • Non-compliant shipments are not permitted to be sold in Canada.

For more information on foodborne illness and safe food handling practices, visit the CFIA website.

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